The radiation model is widely used in traffic demand forecasting. However, when applying the radiation model in the aviation field, it overestimates short-distance travel demand, does not consider flight capacity constraints, and cannot respond well to large-scale disruptions such as COVID-19. Based on the principle of the radiation model, this paper modifies the radiation model using the adjacency matrix of the airline network, along with the total passenger inflow and outflow for each city, flight capacity, and effective distance. The modified radiation model’s performance is verified using the 2018 and 2020 Chinese air passenger flow datasets under normal conditions and large-scale disruptions. The study compared the performance of the modified radiation model with the original radiation model and the opportunity priority selection model on an airline network that includes major cities. The results indicate that the modified radiation model is superior to the original radiation model and opportunity priority selection model in modeling airline networks. Additionally, the passenger travel distances provided by the modified radiation model are more accurate. The modified radiation model can better estimate air traffic demand in airline networks and withstand significant disruptions to airline network traffic.